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There are more nerve cells in one human brain than there are stars in the Milky Way.
Bacteria have flourished on the earth for over three billion years. They were the first life forms on the planet.
Pubic lice (crabs) are usually spread through sexual contact. You cannot catch them by using a public toilet.
A cataract is a clouding of the eyes' natural lens. As we age, some clouding of the lens may occur. The first sign of a cataract is usually blurry vision. Although glasses and other visual aids may at first help a person with cataracts, surgery may become inevitable. Cataract surgery is very successful in restoring vision, and it is the most frequently performed surgery in the United States.
Most childhood vaccines are 90–99% effective in preventing disease. Side effects are rarely serious.